Fiber product



United States Patent O 3,176,437 FIBER PRDUCT Charles E. Lanyon, Troy,N.Y., assignor to John A. Manning Paper Co., Inc., Troy, N.Y. Filed July12, 1962, Ser. No. 209,383 14 Claims. (Cl. 51-408) This inventionrelates to an improved coated abrasive. More particularly, it relates toa coated abrasive Incorporating a backing which resists the distortionoften resulting from application of the various coatings. The finishedproduct also displays an improved resistance to the curling which, inprior products of this type, ensues from differential expansion of thecoating and the backing under varying humidity conditions.

A coated abrasive sheet, or sandpaper as it is commonly known, is madeby applying to one side of a paper backing a heavy coating or adhesive,known as the making coat, usually, but not always, a hot concentratedsolution of hide glue in Water- While the adhesive coat is .still hotand fluid, the abrasive grain is applied and the coated sheet festoonedin racks and partially dried. A second adhesive coat, known as thesizing coat, is then put on to anchor the abrasive grain. The sizingcoat may be the same as the previous coat, i.e., a hot solution of hideglue in water, although more dilute. It

may also be of a different nature such as a synthetic resin. Thecomposite is then festooned, dried and taken down in rolls for furtherprocessing or converting.

`While the material is hanging festooned in the racks, the water in theadhesive coat or coats penetrates through the backing, softening it sothat, because of the weight of the coated material hanging in the loops,it tends to distort. Stresses in the backing are relieved by the rdampening action of the water, which may cause the backing to pucker,cockle, or welt. These defects usually carry through to the finishedroll, resulting in increased waste and scrap.

The trend in the coated abrasive industry is to coat wider and widersheets, but the difculties enumerated increase out of proportion to theincrease in width.

y Therefore, an improved product which would overcome these difficultieswould find a ready sale.

It has been suggested in the prior art to apply a waterimpermeablecoating on the side of the paper designed to receive a subsequentcoating, in order to prevent strikethrough of adhesive or to reducecurl. However, this f expedient forms a surface to which the making coatadheres with difliculty, causing shedding of the abrasiveadhesivecoating from the backing during use.

Accordingly, a principal object of my invention is to provide animproved coated abrasive and an improvedV and will in part appearhereinafter.

The invention accordingly comprises an article of manufacture possessingthe features, properties, and the relation of elements which will beexemplified in the article hereinafter described, and the scope of theinvention will be indicated in the claims.

For a fuller understanding of the nature and objects yof the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing in which:

FIG. 1 is a fragmentary cross section of sheet material ICC used as abacking for a coated abrasive embodying my invention,

FIG. 2 is a fragmentary cross section of a coated abrasive incorporatingthe sheet material of FIG. 1 as a backing,

FIG. 3v is a schematic view of apparatus which may be used inmanufacturing the sheet material of FIG. 1, and

FIG. 4 is a fragmentary cross section of another coated abrasiveembodying the invention.

In general, a coated abrasive embodying my invention includes as abacking a multiply brous sheetkor web of pervious material with animpervious resin or plastic film disposed between a pair of the pliesand preferably located substantially closer to the coated surface of thesheet than to the other surface. The film is suitably bonded to theplies engaging it. Thus, when the surface close to the film is exposedto the glue coats, the glue travels only a short distance through thesheet, the film preventing further penetration. Most of the sheet istherefore unaffected and the sheet as a whole retains its strength andother desirable properties which would otherwise be affected by the wetcoats.

The impervious film is preferably a plastic, since many such materialsdo not interfere with the desirable properties of the final product. Inorder to obtain suflicient strength in the sheet it is generallynecessary that the plastic film be well bonded to the plies on bothsides of it. For this and other reasons, in the case of paper and otherwater-laid products we prefer to use the manufacturing process disclosedby J. Welch et al. in copending application Serial No. 233,508, filedOctober 25, 1962, for Improved Laminated Fiber Product and Method ofMaking It. However, other well-known bonding techniques, e.g.,ofi-machine lamination of paper and preformed resin film, may in manyinstances be used.

It should be noted that the invention is applicable to thermosetting aswell as thermoplastic materials, and the erms plastic and resin, as usedherein, include both types. Plastic and resin are used interchangeablyherein because most plastics are resins. However, it will be understoodthat other materials having plastic properties, e.g., cellulosederivatives, are within the scope of the invention and are thereforeincluded within these terms.

FlG. l illustrates in cross section a 5-ply cylinder sheet 8, used in myinvention. By way of example, the paper sheet may be in a weight basisof 130 pounds per ream (480 X 24 inch X 36 inch), which is a popularweight in the coated abrasives field. The sheet comprises plies 16, l2,14, 16 and 18, with an impermeable film 20 disposed between and bondedto the plies 10 and 12. In further manufacturing processes, the uppersurface 10a of the ply 10 is coated with a water solution of adhesive,the moisture being prevented by the film 20 from reaching the percent ofthe sheet comprising the four plies 12-18.

For example, as shown in FIG. 2, the abrasive layer may be added to thesheet 8 by first applying a making coat 22 to the surface 10a. The waterin the coat 22 saturates the ply fil and thereby weakens it. However,the film 29 prevents it from reaching the bulk of the paper in thesheet, and with the strength of the sheet preserved, distortion thereofduring the later drying operation is largely eliminated. Moreover, thesurface to which the abrasive coating is to be applied is paper. Hence,problems of adhesion of the abrasive coating to my improved sheet are nodifferent than they are with conventional paper.

Following the making coat 22, abrasive grain illustrated at 24 is added,and the grain 24 is covered by a sizing Patented Apr. 6, 1965 of a dandyroll 64, which Y `ond'ply 1'2:is"added at'the i Y y. j 3,176,437...Y

coat Finally, the sheet ishung'to dryas'described above:

The preferred-process Yfor,1nanufacturing the sheet 8 In this Way, avvetv sheet is produced witha layer ofldiscrete particles of resinbetween two wet plies.` The'vvfet Y n method4 should be of aV type{vi/laich,` after it startsl to sheet is-wet pressed anddrieidjaccording to well known n etermined t-,ovbeV` adequate for.Vsoftening and cansingin-A Vcipient ovv in the particular resin used.VIt'is'th'en mimediatelycalendered,k whereupon theresin flows and formsfa continuous nlm internally laminating the Atwo'sheets Y papermakizng'techniquev The dried sheet, still on the L paper, machine, Yis heatedto` a temperature previouslyV lt willbe apparentthat Ythe resinparticles' need not be appliedv at kthe wetend of the paper machine,although this is preferred for reasonsofweconorn'y and also because rasomewhat betterquality product is obtained.

*.Thus, they 'may be appliedto already formed and dried paper webs,which are lthen heated and pressed into a lcontinuous lm. Also, asmentionedpabove, a pre-formed l resin iilrn may be used.

The; resin Aused, to form the film Ztl in theY preferred soften,Vremains very viscous overl a rather extensive'temperaturerrange. Thatis,'the fused resin should retain Y substantial body and Aviscosityafter heating, since, .if it with a bond strength exceeding `theinternalstrength of the two adjacent plies. f Y Y Y FIG. 3 is a'diagrammatic representation of a 5 -Ymold cylinder machinewhichrnay beused in applying the preferredr manufacturing techniquelto multiplyvpaper ernbodying the invention; The machine includes va rseries of vatsSi), 32, 34,. 36 and/48. lSince'the vats rnayhavev an4 identical.construction, Vonlythe'vat y Stlwill be described in detail. Y

Stock consisting of a dilutesuspension 40 of*p'aperf making fibersandWater is introduced into thevat V3f) atV an inlet 42. ltithen owsthrough an arcuate passageway` 44 -arounda' cylinder 46 andv out throughan overflowf 48;@ The cylinder, which is hollowand covered with finewire meshSi), turns with theow of the stock. n y

below the'level 54 vof the stock on the outside by Vmeans of an Youtflowopening 56'. Hence, alpr'essure gradient j exists whichrforces the stocktorow froinvtheoutside of, the cylinder to the'inside'. The ber inthe'stock is trapped n on the wire mesh, thus Vforming the Vply 10,whichnrmoves-f Vout of thevat 30 and is transferred to the' underside of62.- The resin The roll 64 ordinarily takes the Aform of a hollowcylinder:

whose surface isv comprisedof cylinder or Fourdrinier Wire (30480 mesh).i

a traveling wetfelt60 by meanslof a `pressure roll (couch)y fkdispersion is applied at point `by means revolvesin a troughY 66 con- YA becomesV too fluid, it'wills'trik'e into the paper anda continuouslmmay not be produced. Preferably, the temperature at which it becomesiluid is substantially above the Vboiling pointgof lwater, so'thatdrying ofthe paper lcan be readily'accomplished without liquefying theresin.

The particle size is also of importance. The particles `should not betoo fine. Otherwisethey will penetrate the LuV/e'tvveb andnot-formauniform coating of discrete 'resinparticles lfltheyfare too coarse,they may not flow y out under heat andy pressure to develop thev film.

Y organicjperoxidq eg., ldicurnyl peroxidezMixtures of Y v The levelv 52`of water inside thV Cylin'der46 islrrerritl` Vepoxy resinsswith.polyethylene or Ymirrtures of nylon and Amongthe' resinswhichf'inaybe'used for'the 2l) are polyethylene, polypropylene, nylon,,fluorhalocarbona j polycarbonate and epoxy. Mixtures'of these' resinscan `also be. employed. vHow/ever, 'while' a' larger number of :resinsare-usable, we prefer to use, partlybecause of their`low'cost,"pf'clyole'finsA such as polyethylene orpolyprOpylene,extended. with Vfillers and cross-linked with polypropylene vare also'among the preferred materials.

' The preferred;materialsvhave'the addedradvantagesofA producing.flexible, tough sheets which vdo notfrequire The iilinV should notvbe sothin asY to be susceptible to rupture lor so thick as toV cause unduestiffness in the sheet 3; VA thickness rangejof from y0.5 to 5 mils isgenerally acceptable, althoughh we prefer a rangefof V0.5 'to l2 'milsfor sandpaper. j Y 'Y l While itis preferable, for the reasons givenabove, that theVV resin lrn be Vclose to the coatedV surfacefof thebacking, it is not necessary that this be so. Forexample, if

After theapplicationof the resin particles 6:8, theesec-A web 70. Theweb70, in which the paper'plies 10 and 12 sandwich af layer of theparticles, then continues to. Y the vats 34,36 and. 38pwherethe plies14, 16, and 1S are l. l

vat32j' to form a composite.

added. From the Vvat 38, the: webcontinues varound the.'V l

roll 6 2 vassociated therewith and. on to thc-.subsequent papermaking.Voperations. v e erations, including wet pressing, :drying Vandcalendering.

Prior to 'calendering Vthe web The latter are conventional op? bonded tothe plies 10andl2. The strength of the bondj Aformed in thisrnanneris'due in large part'to 'thef fact that the i'lbers ofthe plies 19 .and12 penetrate into thel vplastic film 20 (FIG. l) and are gripped by thefilm which is,"in essence, `formed around them.

VIf'desired, the resin suspension rnay'also bevfappliedsat point X bymeans of a spraying device or other suitable method.` Thearnountof resinthat is appliedcan be conf Y trolled byV varying the concentration ofthe suspension in the trough 66; by Vchanging the characteristics of theY dandy'roll 64, if this is used; by changing the spraying pressure,if'uthis method of application is preferred; or A by other means whichare obvious to' those skilled in the' art. e

the -film is centrally Alocated within the sheet, over 50 percentofrtheydry strength ofthe backing is retained when thecoating is applied. Y n*l Y Y Insome cases it Will be advantageous .to incorporate a secondresin film near the uncoatedv surface of the back ing. Thisprovides ameans of controlling therate of Vmoisturev vapor penetration'intoy thesheet and regulating its curling propensities;` `FIG. 4 shows` acoatedabrasive utilitzing'lsuch a sheet '74 'incorporating a secondresin film 76'near the'surfacek 74a remote from the abrasive grains`2'4".. Specifically, 'the coated abrasive, which isvsimilar tothecoatedabrasive of FIG. 2,1`comprisesvplies 1G, 12,' lala and 18 with' the tilm20 between the plies 1t? and 12 andtheV film 16 disposed between andbonded to the plies E aud 13. The'nialring coaty 22 and the sizing coatZe'anch'or the abrasive grains 24 to the 4outer ksurface of the plylli). v

.Arjs'peciiic' exampleof a.' coated abrasive, embodying myinventicnrwillnow be described in detail, it being understood,thatnrthis examplerisgivenby vwayvof illustrationand not limitationlof the invention. i

VThe iiber'furni'sh for thebackingrnay consist of rope, jute, woodpulp,V cotton orfmixtures of these. Therevquired lamounts of the fibrousconstituents are introduced into a beaterA and beaten to the requisitedegree.V In the Ybeaterr thejber 'may also beV dyedV and additives suchas resin size, elastomers, etc., maybe-added. After beating, 4thematerial "is droppedV to storage chests and` passed s, 17e/asv throughJordans to a paper machine which may be a 5- mold cylinder machine asillustrated in FIG. 3.

'The paper machine is adjusted to provide a backing sheet weighing 130pounds per ream (48() sheets, 24 inch x 36'inch). In the vat 30, theconsistency of the stock is set so that, at the speed selected, a plyweighing about 26 pounds is formed. This constitutes about 20 percent'of the total weight of the fiber furnish. At the point X,

a water suspension of finely divided resin particles 68 is applied inthe manner described above. The particles are of polyethylene resinmanufactured by United States lndustrial Chemical Co. and marketed underthe trade designation Microthene 700. They are ground to pass through ascreen having 150 openings per lineal inch, and the concentration of thefinely divided polyethylene in the water is about 9 percent. At thespeed selected, this concentration results in the application of about1.8 grams of resin per square foot of paper. A

After drying, the web 70 is heated to a temperature of 275 F. and thencalendered under a pressure of 100 lbs. per lineal inch. Under thecalendering pressure, the resin particles fuse and form a film about 0.8mil thick.

The paper is then slit to width and coated with abrasive. To accomplishthis, a heavy coat of hot concentrated hide glue is first applied to thecoat side of the backing (i define the coat side as that surface (10a)of the sheet S closest to the impermeable film While the glue is stillhot and fluid, abrasive grain is applied by conventional methods. Thecomposite is then festooned in racks and partially dried. A more dilutesolution of hot hide glue is then applied to the abrasive coat to anchorand hold the grain in place, after which the composite is againfestooned in racks and dried. Finally, it is taken down in rolls forfurther processing.

Coated abrasives made according to the present invention are handledwith much less trouble through the coating operation, during drying andthrough subsequent operations. The bulk of the backing remains dry andretains body and stiffness. Distortion, wrinkling and puckering arenoticeably less with the improved backing than with conventional paper.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above article without departingfrom the scope of the invention, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention, which, as amatter of language, might be said to fall therebetween.

I claim:

l. A coated abrasive comprising abrasive grains anchored by an adhesiveto a fibrous backing comprised of multiple fibrous layers and a resinfilm between and bonded to first and second ones of said layers saidadhesive being contiguous with a fibrous layer of said back-- ing andanchoring said grains directly thereto.

2. The article defined in claim l in which said film is substantiallycloser to a first surface of said backing to which said grains areanchored than to a second surface opposite said first surface.

3. The article defined in claim 1 in which the fibers in said first andsecond layers penetrate into said film.

4. The article defined in claim 3 in which said first and second layersare integral.

5. The article defined in claim l including at least five fibrouslayers, said first layer being adjacent to said grams.

6. The articie defined in claim l including at least three of saidlayers, said layers having substantially equal thicknesses, there beinga fewer said layers on the side of said film facing said grains than 0nthe other side of said film.

7. A coated abrasive comprising abrasive grains anchored by an adhesivedirectly to a fibrous layer of a backing comprised of multiple fibrouslayers, said backing including a first resin film close to a surface ofsaid backing to which said grains are anchored and a second resin filmclose to the opposite surface of said backing, each of said films beingdisposed between and bonded to an adjacent pair of said layers.

8. The article defined in claim 7 in which said backing is comprised ofpaper.

9. The articie defined in claim 8 in which the fibers in the layersadjacent to said film penetrate into said film.

10. In a coated abrasive of the type comprising abrasive grains anchoredto a paper backing by a glue having a paper-weakening base of water orthe like, the improvement in which said backing comprises a plurality ofpaper layers and a resin film disposed between and bonded to first andsecond ones of said layers, said glue being contiguous with said firstfibrous layer of said paper backing and anchoring said abrasive grainsdirectly thereto.

1l. The article defined in claim l0 in which said film is substantiallycloser to a first surface of said backing to which said grains areanchored than to a second surface opposite said first surface.

12. The article defined in claim ll including a second resin filmdisposed between and bonded to a pair of said v layers, said second filmbeing substantially closer to said second surface than to said firstsurface.

13. The article defined in claim 10 in which a substantial portion ofthe fibers in said first and second layers penetrate into said film.

14. The article defined in claim 13 in which said first and secondlayers are integral with each other.

FRANK H. BRONAUGH, LESTER M. SWINGLE,

Examiners.

1. A COATED ABRASIVE COMPRISING ABRASIVE GRAINS ANCHORED BY AN ADHESIVETO A FIBROUS BACKING COMPRISED OF MULTIPLE FIBROUS LAYERS AND A RESINFILM BETWEEN AND BONDED TO FIRST AND SECOND ONES OF SAID LAYERS SAIDADHESIVE BEING CONTIGUOUS WITH A FIBROUS LAYER OF SAID BACKING ANDANCHORING SAID GRAINS DIRECTLY THERETO.